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Title: The microbial ecology of Sub-Antarctic tundra soils
Author: Smith, M. J.
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1983
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The microbial ecology of tundra soils was studied at four contrasting sites on the sub-Antarctic island of South Georgia. Two main study sites were used - a deep Mossbank dominated by Polytrichum alpestre/Chorisodontium aciphyllum and a Festuca contracta Grassland, and two subsidiary sites - a dense stand of the deciduous Dwarf Shrub Acaena magellanica and a Tortula robusta/Rostkovia magellanica Mire included for certain aspects of this two year programme. The viable bacterial and fungal populations of the main sites were comparable to those of other tundra regions and showed a similar decrease with depth. Intra-site variability was correlated with vegetation cover and increased microbial populations associated with Juncus scheuchzerioides at the Mossbank and Festuca contracta at the Grassland. Seasonal variability of the microbial populations showed complex correlations with a range of edaphic variables of which temperature and moisture were the most important. Direct bacterial counts showed high numbers present. Variability in total numbers was reflected in the viable counts. Cellulolytic bacteria and fungi and ligninolytic fungi, a small but consistent part of the microbial populations, were correlated with depth, moisture and the heterotrophic populations but showed little association with the vegetation cover. Chrysosporium sp. and pycnidial fungi were important celluloytic organisms found at both main sites. Sterile mycelia were frequently isolated. The decomposition of moribund moss in the Mossbank was very slow (3-5% p.a.) while dead grass culms in the Grassland showed rates of 15-20% p.a. The decomposition rates of a pure cellulose material were compared at all four sites and showed the order of cellumlytic activity to be: Dwarf Shrub>Mire>Grassland>Mossbank. Patterns of cellulose decomposition revealed differences between the sites with depth and season and correlation analyses showed associations with vegetation at the Grassland and Mire sites. Total potential activity of the four sites was assessed by respirometry. The expression of results was complicated by the differing organic contents of the soils. The Dwarf Shrub and Mire sites showed consistently greater oxygen consumption than the Grassland or Mossbank and all sites showed reduced respiration with depth. Correlation analyses showed moisture to be the most important seasonal factor and at the Mossbank respiration was correlated positively with J. scheuchzerioides and negatively with P. alpestre. A general model linking decompositioA and nutrien~ cycling was created.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Ecology